I understand, this is an unexpected behavior. Since you were able to compile your code successfully using mraa 1.4.0 + upm 0.8.0, I'd suggest you to go back to these versions. You can do so, by following these instructions:

Now you will have mraa 1.4.0 + upm 0.8.0 and you'll be able to continue working with your application. As I mentioned this behavior is not usual, so, I suggest you to report it in upm's Github (https://github.com/intel-iot-devkit/upm/issues).